1. Field of the Invention
The present invention relates to an electronic device and a control method.
2. Description of the Related Art
Recent imaging apparatuses, which are typified by digital cameras, have a function of recording not only still images but also moving images with sound. That is to say, a moving image obtained by successively imaging an object on a time axis can be recorded together with data of sound around the object in a storage medium such as a memory card. Sound to be recorded, such as the sound around the object, will be hereinafter referred to as “environmental sound”.
The imaging apparatuses can focus and zoom in on an object during imaging by moving an optical lens. However, a driving sound is generated at the time of driving for moving the optical lens. Housings of the recent digital cameras have been becoming smaller and smaller, and the distance between the source of the driving sound and a microphone in each digital camera is short. For this reason, the microphone in the digital camera acquires the driving sound, and as a result, the driving sound is likely to become noise, which overlaps the environmental sound.
Conventionally, a technique called a “spectral subtraction method” for reducing the aforementioned noise is known in Japanese Patent Laid-Open No. 2006-279185. This spectral subtraction method will now be briefly described with reference to FIG. 21. FIG. 21 is a part of a block configuration of a digital camera. This apparatus is constituted by a control unit 2109 that controls the overall apparatus, an operation unit 2110 that accepts an instruction from a user, an optical lens, a lens control unit, and the like. Furthermore, this apparatus is constituted by an imaging unit 2101 that performs imaging and obtains image data, a microphone 2205, an audio input unit 2102 that acquires sound as audio data, and a memory 2103 that stores the image data and the audio data. Note that the image data and the audio data stored in the memory 2103 are usually subjected to a coding process and stored as coded data in a storage medium.
In a time period in which a moving image with sound is recorded, upon the control unit 2109 detecting an instruction to zoom in or zoom out or the like from a user via the operation unit 2110, the control unit 2109 controls the imaging unit 101 so as to change the position of the optical lens. In accordance with this, the imaging unit 2101 drives a driving source such as a motor in order to change the position of the optical lens. At this time, the microphone 2205 picks up the driving sound of the optical lens, and the sound data consequently obtained from the microphone 2205 is data in which the environmental sound and the driving sound (noise) are combined. The audio input unit 2102 shown in FIG. 21 has a function of reducing this driving sound.
The sound detected by the microphone 2205 is converted into 16-bit digital data (hereinafter referred to as sound data) at a sampling rate of 48 kHz, for example, by an ADC (analog-digital converter) 2206. An FFT 2207 performs an FFT (fast Fourier transform) process on the sound data (e.g., 1024 samples of sound data) arrayed in time series to convert the sound data into data at each frequency (amplitude spectrum). A noise reduction unit 2200 performs a noise reduction process by subtracting noise data at each frequency from data at the corresponding frequency. For this reason, the noise reduction unit 2200 has a profile storing unit 2210 that stores, in advance, amplitude data (noise profile) of noise at each frequency, and an amplitude spectrum subtracting unit 2211. The amplitude spectrum subtracting unit 2211 subtracts amplitude data of noise at each frequency recorded in the profile storing unit 2210 from the amplitude spectrum. Thereafter, the amplitude spectrum from which the noise has been subtracted is subjected to an inverse FFT process at an IFFT 2214, and is reverted to original time-series sound data. Thereafter, an audio processing unit 2216 performs various processes on this sound data. Then, an ALC (auto level controller) 2217 adjusts the level of the sound data, and a result thereof is stored in the memory 2103.
The summary of the “spectral subtraction method” is as described above. As mentioned above, it is desirable that the noise profile stored in advance in the profile storing unit 2210 represents the driving sound that is actually generated in the imaging unit 2101.
In the case of applying the technique described in Japanese Patent Laid-Open No. 2006-279185 to an imaging apparatus, an error occurs between the driving sound that is actually generated in the imaging apparatus and the driving sound indicated by the noise profile stored in advance, due to the following factors.                An individual difference in sound noise generation in drive units such as a motor and a gear        A difference in sound noise due to an assembled state of the imaging apparatus        A difference in sound noise due to a zoom position        Abrasion and aged deterioration of parts        Temperature conditions at the time of operation        Posture of the imaging apparatus        Replacement of parts in the drive unit or the recording unit after the apparatus is shipped to market, as in the case of handling a failure        
For this reason, it is difficult to reduce noise using one noise profile stored in advance, and there has been a problem in that it is difficult to acquire sound from which noise has been accurately reduced.